This invention relates to an image receiving layer for the dye diffusion transfer containing a mordant which consists of a crosslinked reaction product of a watersoluble cationic polymer having recurrent units containing a quaternary nitrogen atom and carrying free glycidyl groups.
Such image-receiving layer may be coated onto a support layer and may be part of a light-insensitive image receptor sheet whic is to be contacted for development with a light-sensitive element comprising at least one light-sensitive silver halide emulsion layer and an associated dye-giving compound capable of releasing on development an imagewise distribution of a diffusible dye. Alternatively such image receiving layer may also be an integral constituent of a monosheet material comprising a light-sensitive element and an image receptor element.
It is well known in the field of photography to use various polymers as mordants for the mordant layers of photographic materials which are composed of a support layer, at least one silver halide emulsion layer, at least one layer which produces an image dye and is in contact with said silver halide emulsion layer, and a so-called integrated image receiving layer. Polymers suitable for the preparation of mordant layers have been described, for example, in U.S. Pat. No. 3,709,690; these polymers are obtained by the quaternisation of a polymer which contains tertiary nitrogen atoms with an alkylating agent or aralkylating agent.
Water insoluble polymers which are prepared by the reaction of polymers containing chloromethyl groups with tertiary amines and which can be crosslinked as described in U.S. Pat. No. 3,859,096 have been described as mordants in German Offenlegungsschrift No. 2,445,782. One disadvantage of using such mordants in instant image photography is that the mordanted image dyes tend to migrate from the image areas into non-image areas. This migration of dye, which is due to the fact that the mordant does not fix the dye firmly enough, results in reduced colour densities and chromatic fringes, particularly if the moisture content is high.
A further disadvantage of the mordants described in German Offenlegungsschrift No. 2,445,782, is that when image dyes which have been mordanted on these substances are exposed to sunlight, they undergo bleaching to a greater degree than in the unmordanted state and the overall light resistance of dye images obtained on such mordants is low. Furthermore, the use of water insoluble polymers as mordants for the preparation of mordant layers gives rise to particular difficulties if gelatine is used as binder. Water soluble polymeric mordants having molecular weights above 50,000 cause an undesirable increase in viscosity in aqueous solution due to their high content of quaternary ammonium groups.
Cationic polyurethanes have been mentioned as mordants for anionic organic compounds, in particular dyes, for example in German Offenlegungsschrift No. 2,315,304. The polymers described in the said document have average molecular weights of between 10,000 and 60,000 depending on the stoichiometric proportions of the reactants used for their preparation.
Mordants of this kind are generally unsuitable for the purposes of this invention. Although they are sufficiently resistant to diffusion if they have average molecular weights above 20,000, they either fail to take up the dye from the alkaline processing medium or take it up too slowly. With average molecular weights below 20,000, their dye absorption capacity is satisfactory but they have insufficient resistance to diffusion for the purposes of the invention.